PA1621 Maintenance Manual All Series | January 2017
7.2 HEIGHT CONTROL VALVES
The height control valves automatically add air
to, or release air from air springs to maintain
constant suspension height regardless of load,
or load distribution. Each valve adjusts
independently according to the following
conditions:
Loading position
As the load increases and lowers the vehicle
body, the control arm commands the height
control valve to add air to air springs.
Neutral position
When vehicle body reaches the normal ride
height, the height control valve control arm
reaches the "neutral" position and keeps both
the supply and exhaust ports closed to ensure
normal ride height is maintained. This condition
remains static until the vehicle load is altered.
Unloading position
As the load decreases and raises the vehicle
body, the control arm commands the height
control valve to release air from air springs.
FIGURE 43: HEIGHT CONTROL VALVE 16093
7.3 MAINTENANCE
The height control valve requires no periodic
maintenance. Height control valve linkage
operates on rubber bushings and no lubrication
should be attempted at this point. Inspect the
valve for loose joints, air leaks and worn
bushings.
7.3.1 Removal and installation
Before disconnecting any height control valve air
lines, securely support the vehicle by its jacking
points on the body, and place safety support
underneath body. Refer to "VEHICLE JACKING
POINTS" in Section 18, "Body".
1. Exhaust air from air system by opening the
drain cock on accessory air reservoir.
Remove height control valves.
2. Disconnect overtravel lever from link and
pull down lever to exhaust remaining air from
air springs.
3. Disconnect air supply and delivery lines from
the height control valve. Cover ends of the
lines with tape to prevent entry of foreign
matter.
4. Remove the nuts retaining the height control
valve to the mounting bracket, then remove
valve assembly.
Note: The height control valve bolts
equipped with a nylon insert should be
replaced after the third (3rd) tightening.
Reverse removal procedure to replace height
control valve. After installation, check for leakage
using a soap and water solution.
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